class ResourceRoutes

class ResourceRoutes implements EventSubscriberInterface {
    
    /**
     * The plugin manager for REST plugins.
     *
     * @var \Drupal\rest\Plugin\Type\ResourcePluginManager
     */
    protected $manager;
    
    /**
     * The REST resource config storage.
     *
     * @var \Drupal\Core\Entity\EntityStorageInterface
     */
    protected $resourceConfigStorage;
    
    /**
     * A logger instance.
     *
     * @var \Psr\Log\LoggerInterface
     */
    protected $logger;
    
    /**
     * Constructs a RouteSubscriber object.
     *
     * @param \Drupal\rest\Plugin\Type\ResourcePluginManager $manager
     *   The resource plugin manager.
     * @param \Drupal\Core\Entity\EntityTypeManagerInterface $entity_type_manager
     *   The entity type manager
     * @param \Psr\Log\LoggerInterface $logger
     *   A logger instance.
     */
    public function __construct(ResourcePluginManager $manager, EntityTypeManagerInterface $entity_type_manager, LoggerInterface $logger) {
        $this->manager = $manager;
        $this->resourceConfigStorage = $entity_type_manager->getStorage('rest_resource_config');
        $this->logger = $logger;
    }
    
    /**
     * Alters existing routes for a specific collection.
     *
     * @param \Drupal\Core\Routing\RouteBuildEvent $event
     *   The route build event.
     *
     * @return array
     */
    public function onDynamicRouteEvent(RouteBuildEvent $event) {
        // Iterate over all enabled REST resource config entities.
        
        /** @var \Drupal\rest\RestResourceConfigInterface[] $resource_configs */
        $resource_configs = $this->resourceConfigStorage
            ->loadMultiple();
        foreach ($resource_configs as $resource_config) {
            if ($resource_config->status()) {
                $resource_routes = $this->getRoutesForResourceConfig($resource_config);
                $event->getRouteCollection()
                    ->addCollection($resource_routes);
            }
        }
    }
    
    /**
     * Provides all routes for a given REST resource config.
     *
     * This method determines where a resource is reachable, what path
     * replacements are used, the required HTTP method for the operation etc.
     *
     * @param \Drupal\rest\RestResourceConfigInterface $rest_resource_config
     *   The rest resource config.
     *
     * @return \Symfony\Component\Routing\RouteCollection
     *   The route collection.
     */
    protected function getRoutesForResourceConfig(RestResourceConfigInterface $rest_resource_config) {
        $plugin = $rest_resource_config->getResourcePlugin();
        $collection = new RouteCollection();
        foreach ($plugin->routes() as $name => $route) {
            
            /** @var \Symfony\Component\Routing\Route $route */
            // @todo: Are multiple methods possible here?
            $methods = $route->getMethods();
            // Only expose routes that have an explicit method and allow >=1 format
            // for that method.
            if ($methods && ($method = $methods[0]) && $rest_resource_config->getFormats($method)) {
                $route->setRequirement('_csrf_request_header_token', 'TRUE');
                // Check that authentication providers are defined.
                if (empty($rest_resource_config->getAuthenticationProviders($method))) {
                    $this->logger
                        ->error('At least one authentication provider must be defined for resource @id', [
                        '@id' => $rest_resource_config->id(),
                    ]);
                    continue;
                }
                // Check that formats are defined.
                if (empty($rest_resource_config->getFormats($method))) {
                    $this->logger
                        ->error('At least one format must be defined for resource @id', [
                        '@id' => $rest_resource_config->id(),
                    ]);
                    continue;
                }
                // The configuration has been validated, so we update the route to:
                // - set the allowed response body content types/formats for methods
                //   that may send response bodies (unless hardcoded by the plugin)
                // - set the allowed request body content types/formats for methods that
                //   allow request bodies to be sent (unless hardcoded by the plugin)
                // - set the allowed authentication providers
                if (in_array($method, [
                    'GET',
                    'HEAD',
                    'POST',
                    'PUT',
                    'PATCH',
                    'DELETE',
                ], TRUE) && !$route->hasRequirement('_format')) {
                    $route->addRequirements([
                        '_format' => implode('|', $rest_resource_config->getFormats($method)),
                    ]);
                }
                if (in_array($method, [
                    'POST',
                    'PATCH',
                    'PUT',
                ], TRUE) && !$route->hasRequirement('_content_type_format')) {
                    $route->addRequirements([
                        '_content_type_format' => implode('|', $rest_resource_config->getFormats($method)),
                    ]);
                }
                $route->setOption('_auth', $rest_resource_config->getAuthenticationProviders($method));
                $route->setDefault('_rest_resource_config', $rest_resource_config->id());
                $parameters = $route->getOption('parameters') ?: [];
                $route->setOption('parameters', $parameters + [
                    '_rest_resource_config' => [
                        'type' => 'entity:' . $rest_resource_config->getEntityTypeId(),
                    ],
                ]);
                $collection->add("rest.{$name}", $route);
            }
        }
        return $collection;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function getSubscribedEvents() {
        $events[RoutingEvents::DYNAMIC] = 'onDynamicRouteEvent';
        return $events;
    }

}